Does the Number of Pharmacies a Patient Frequents Affect Adherence to Statins?

BACKGROUND: We hypothesized that medication adherence is affected by the number of pharmacies a patient frequents. OBJECTIVES: The objective was to estimate the strength of association between the number of pharmacies a patient frequents and adherence to statins. METHODS: Using administrative data from the Nova Scotia Seniors' Pharmacare program, a retrospective cohort study was conducted among subjects aged 65 years and older first dispensed statin between 1998 and 2008. The Usual Provider of Care (UPC), was defined as the number of dispensation days from the most frequented pharmacy divided by the total number of dispensation days. Estimated adherence of over 80% of the Medication Possession Ratio was defined as adherent. Data were analyzed using hierarchical linear regression. RESULTS: The cohort of 25,641 subjects was 59% female with a mean age of 74 years. During follow-up, subjects filled prescriptions in a median of 2 (mean = 2; standard deviation = 0.88) pharmacies and visited pharmacies a median of 28 (mean = 30) times. During that time, 61% of patients used one pharmacy exclusively. Among subjects using 1 pharmacy, 59% were adherent while 58% using more than one pharmacy were adherent. However, upon adjustment for differences in distributions of age, sex, and other confounders, subjects who used more than one pharmacy had 10% decreased odds of statin adherence (odds ratio: 0.90, 95% confidence interval: 0.86-0.96). These results were robust in sensitivity analyses. CONCLUSIONS: Among seniors newly starting statin therapy, using a single community pharmacy was modestly associated with adherence.